- Oct 30, 2017 -
The walkie-talkie can be used for contact and command scheduling among group members to improve communication efficiency and improve the ability to respond quickly to emergencies. There are also some special occasions to use the walkie-talkie, such as explosion-proof walkie-talkie, waterproof walkie-talkie, police walkie-talkie and so on. The car station can also be included in the use of radio.
Walkie-talkie technology first produced in the twilight of the twilight, was born in Westinghouse's laboratory. A man named John Kermode's eccentric inventor "whimsical" wanted to automate the seizure of postal documents, and every idea of electronic technology was very novel. His idea is to do the radio on the envelope mark, the information in the walkie-talkie is the recipient's address, like today's postal code. Kermode invented the earliest radio logo, the design is very simple, that is, a "bar" that the number "1", two "bar" that the number "2", and so on. Then he invented the intercom reading device consisting of the basic components: a method (which can emit light and receive reflected light) to measure the reflected signal strip and the empty method, ie the edge locating coil; and the method of using the measured result, Encoder.
The working principle of the walkie-talkie is as follows:
1, the launch part:
Phase-locked loop and voltage-controlled oscillator (VCO) to generate the radio frequency carrier signal, through the buffer amplification, excitation amplification, power amplifier, the rated RF power, through the antenna low-pass filter to suppress the harmonic components, and then launched through the antenna The
2, the receiving part:
The receiving section mixes the amplified signal from the radio frequency with the first local oscillator signal from the phase locked loop frequency synthesizer circuit at the first mixer and generates a first intermediate frequency signal. The first intermediate frequency signal further eliminates the adjacent channel clutter signal through the crystal filter. The filtered first intermediate frequency signal enters the intermediate frequency processing chip and is again mixed with the second localized signal to generate the second intermediate frequency signal. The second intermediate frequency signal is filtered out by a ceramic filter to filter the unwanted spurious signal, Generate an audio signal. Audio signal through the amplification, bandpass filter, de-emphasis and other circuits, into the volume control circuit and power amplifier amplification, drive the speaker, get the information people need.
3, modulation signal and modulation circuit:
The voice of a person is converted into audio by a microphone
4, signaling processing:
CPU generates CTCSS / CDCSS signal through the amplification adjustment, into the voltage-controlled oscillator for modulation. After receiving the low frequency signal obtained by frequency discrimination, some of the amplified and sub-audio band-pass filter for filtering and shaping, into the CPU, compared with the default value, the results control the audio amplifier and speaker output. That is, if the same as the preset value, then open the speaker, if different, then turn off the speaker.